Novel agents for managing dyslipidaemia

Triglyceride-lowering trials

PURPOSE OF REVIEW

We provide an overview of current evidence about the independent role of high triglyceride levels for cardiovascular risk and for acute pancreatitis.

RECENT FINDINGS

Natural experiments of Mendelian randomization have given us a deeper understanding about the molecular pathways involved in triglyceride metabolism. Individuals with low-triglyceride levels generally have lower rates of cardiovascular disease (CVD). There has been a significant growth in the development of new agents that modulate enzymes involved in a variety of aspects of triglyceride packaging into VLDL or chylomicron particles, and triglyceride catabolism. Antisense inhibitors of apolipoprotein CIII are being tested, as are a variety of agents designed to increase lipoprotein lipase activity. Large-scale trials are underway with purified fatty acid (FA) formulations in over 20 000 individuals in aggregate. A large study of a new fibrate is underway.

SUMMARY

A focus on patients with elevated triglyceride levels is a new paradigm not previously the focus of large trials. Clinical outcome data on cardiovascular risk reductions remains sparse. Some drugs are already approved for use in rare inherited disorders predisposing to severe hypertriglyceridaemia and acute pancreatitis. Safety and costs issues are critical.

Therapeutic targets: progress of their exploration and investigation of their characteristics

Modern drug discovery is primarily based on the search and subsequent testing of drug candidates acting on a preselected therapeutic target. Progress in genomics, protein structure, proteomics, and disease mechanisms has led to a growing interest in and effort for finding new targets and more effective exploration of existing targets. The number of reported targets of marketed and investigational drugs has significantly increased in the past 8 years. There are 1535 targets collected in the therapeutic target database compared with approximately 500 targets reported in a 1996 review. Knowledge of these targets is helpful for molecular dissection of the mechanism of action of drugs and for predicting features that guide new drug design and the search for new targets. This article summarizes the progress of target exploration and investigates the characteristics of the currently explored targets to analyze their sequence, structure, family representation, pathway association, tissue distribution, and genome location features for finding clues useful for searching for new targets. Possible "rules" to guide the search for druggable proteins and the feasibility of using a statistical learning method for predicting druggable proteins directly from their sequences are discussed.

Pharmacological regulation of low density lipoprotein receptor expression: Current status and future developments

Plasma levels of low-density lipoprotein (LDL) cholesterol are considered to be a major risk factor for the development of cardiovascular diseases. The LDL receptor is the key component in the maintenance of cholesterol homeostasis in the body, playing a pivotal role by regulating the hepatic catabolism of LDL cholesterol. Many clinical studies using statins, which up-regulate the LDL receptor expression via a feedback mechanism, have demonstrated that the reduction of LDL cholesterol levels lowers the incidence of cardiovascular events in both primary and secondary prevention. In this context, new strategies designed to increase hepatic LDL receptor activity can be considered as attractive opportunities for future therapy. Several potential new drugs have been described in the last decade to up-regulate LDL receptor expression in vitro and in vivo, thus allowing the identification of new transcriptional and post-transcriptional mechanisms.

Ezetimibe/Simvastatin: a review of its use in the management of hypercholesterolemia

Ezetimibe/simvastatin (Inegy, Vytorin) therapy combines two lipid-lowering compounds with complementary mechanisms of action, thereby blocking the two sources of plasma cholesterol and improving lipid profiles. Thus, intestinal absorption of dietary cholesterol and related phytosterols is blocked by ezetimibe, with the biosynthesis of cholesterol in the liver inhibited by simvastatin. Developing management trends for primary hypercholesterolemia include the aggressive reduction of low-density lipoprotein cholesterol (LDL-C) to goals lower than previously considered appropriate, the targeting of lipid subfractions and atherogenic indices other than LDL-C alone, and the broader use of combination lipid-lowering therapy. In line with these trends, ezetimibe/simvastatin is an effective and generally well tolerated adjunct to dietary therapy for markedly reducing LDL-C levels, providing a 52% reduction with the recommended starting dosage. Furthermore, ezetimibe/simvastatin is formulated with variable doses of simvastatin (i.e. 10/10 mg, 10/20 mg, 10/40 mg, and 10/80 mg) and hence, the dosage may be adjusted to suit the individual patient's needs. As longer-term efficacy, tolerability, economic and outcome data accrue, ezetimibe/simvastatin will be positioned more definitively relative to existing and emerging lipid-lowering treatments. Currently, ezetimibe/simvastatin therapy represents a valuable novel option for the management of primary hypercholesterolemia across diverse patient populations and as an adjunct to other lipid-lowering treatments in those with homozygous familial hypercholesterolemia.

Oleylethanolamide regulates feeding and body weight through activation of the nuclear receptor PPAR-alpha

Oleylethanolamide (OEA) is a naturally occurring lipid that regulates satiety and body weight. Although structurally related to the endogenous cannabinoid anandamide, OEA does not bind to cannabinoid receptors and its molecular targets have not been defined. Here we show that OEA binds with high affinity to the peroxisome-proliferator-activated receptor-alpha (PPAR-alpha), a nuclear receptor that regulates several aspects of lipid metabolism. Administration of OEA produces satiety and reduces body weight gain in wild-type mice, but not in mice deficient in PPAR-alpha. Two distinct PPAR-alpha agonists have similar effects that are also contingent on PPAR-alpha expression, whereas potent and selective agonists for PPAR-gamma and PPAR-beta/delta are ineffective. In the small intestine of wild-type but not PPAR-alpha-null mice, OEA regulates the expression of several PPAR-alpha target genes: it initiates the transcription of proteins involved in lipid metabolism and represses inducible nitric oxide synthase, an enzyme that may contribute to feeding stimulation. Our results, which show that OEA induces satiety by activating PPAR-alpha, identify an unexpected role for this nuclear receptor in regulating behaviour, and raise possibilities for the treatment of eating disorders.